An offset printer including a plate making section which is implemented by an electrophotographic procedure and an offset printing section is known in the art. With such a printer, it has been customary to arrange the plate making section and the printing section side by side by considering the fact that charging, exposing, developing and fixing processes involved in electrophotographic printing are apt to increase the overall dimensions of the printer and the fact that toner, or developer, is apt to be scattered around. Hence, a substantial space has to be allocated to the plate making section and, moreover, a plate produced by the plate making section has to be loaded in the printer by hand. The electrophotographic procedure processes an image by analog signal processing and therefore is not suitable for use as an output terminal of a computer or similar digital apparatus.
Generally, the printing section of the above-described type of offset printer is made up of a plate drum for wrapping a plate therearound, a rubber drum to which an image is to be transferred from the plate, and a press drum for clamping and transporting a paper to which the image is to be transferred from the rubber roller. The rubber roller is disposed obliquely below the plate drum, and the press drum is disposed obliquely below the rubber drum. An image is transferred from the rubber drum to the paper in a nipping section which is defined between the press drum and the rubber drum. Immediately after the press roller unclamps the paper, the paper with the image is driven out of the printer by way of a discharge pawl and a discharge roller. A problem with such a prior art offset printer is that when the paper has a substantial length, the trailing edge of the paper remains nipped in the nipping section by the press and rubber drums when the leading edge of the paper is released from the press drum. In such a condition, the leading edge of the paper is apt to spring back toward and adhere to the rubber drum due to ink which is deposited on the rubber drum, jamming the paper transport path of the printer. While various attempts have heretofore been made to eliminate such an occurrence, each of them has both merits and demerits.